How to build RAM size >2^N for an N-bit computer?

How to build RAM size >2^N for an N-bit computer?

In the present architecture, it seems that the maximum size of RAM that you can build is limited by the width of our bus, which here is 2^16=65536. What do you do if you need/want more RAM in such an architecture? Every time I try to think of a solution, it feels like I'm going to have to greatly increase the complexity of the overall architecture; is that correct? Is there a software solution?